Sensor apparatus for metal particles in fluids

ABSTRACT

3. FIG. 1.

The invention relates to a device having a sensor device for detecting a contamination in the form of metal particles in a fluid, which is at least partially encompassed by a partition wall, which is at least partially penetrated via a receiving opening by the sensor device arranged in its functional position and comprising its sensor detecting the metal particles, wherein the sensor device can be removed from the partition wall into an inoperative functional position, in particular for maintenance or replacement purposes.

Sensor devices of this type are state of the art, see EP 0 893 683 B1. Sensor devices of this type are used in particular in fluid systems, in which fluids, such as hydraulic oils or lubricating oils, flow through assigned system components, e.g. hydraulic pumps and hydraulic motors or gearboxes. These system components are subject to wear, contaminating the fluid with metal particles. These particles can settle in valves, in bearings lubricated by the fluid or other components and cause damage there. The known sensor devices permit the detection of the contamination or a degree of contamination of the fluids with metal particles by determining the electrical resistance between two adjacent electrodes, wherein said electrical resistance is dependent on the presence of metal particles between the electrodes.

In the state of the art, as with the solution described in EP 0 893 683 B1, a magnetic field is provided to collect ferromagnetic particles on the sensor device. An electrical signal generated on the basis of the determined resistance can be used to switch off the fluid system as soon as the degree of contamination has exceeded a predetermined threshold value, or to generate an alarm signal.

For reason inherent in the system, such sensor devices require maintenance. In particular, after an aggregation of metal particles between the electrodes of the sensor, a cleaning process or a replacement has to be performed, for which the sensor device has to be removed from the wall separating the fluid area from the sensor, e.g. from a pipe wall, container wall or gearbox housing wall. Because it is normally impractical to empty the fluid area for the respective maintenance process, removing the sensor device from the partition wall is extremely problematic and may pose an environmental hazard because of fluid leakage.

With regard to this problem, the invention addresses the object of providing a sensor device of the type mentioned at the beginning, which is characterized by an improved operational behavior.

According to the invention, this object is solved by a sensor device having the features of claim 1 in its entirety.

According to the characterizing part of claim 1, the invention is characterized in that the sensor device interacts with a closing device such that upon removal of the sensor device to its inoperative functional position, the closing device closes the receiving opening and, in the opposite direction, when the sensor device is brought into its functional position, releases this receiving opening. Because the process of removing the sensor device from the partition wall in this way results in the closure of the receiving opening by means of the closing device and thus eliminates the problem of fluid leakage, maintenance or replacement work is simple and safe without any risk of environmental pollution.

In a particularly advantageous manner, the closing device can have a spring-loaded closing plate forming a kind of check valve, wherein said closing plate can be brought into an open position releasing the receiving opening under the action of the sensor device against the action of its closing spring or into its blocking position blocking the receiving opening under the action of the closing spring. In this way, a closing device, which closes automatically when the sensor device is removed, can be implemented in a particularly simple construction.

In particularly advantageous embodiments, the receiving opening in the partition wall is delimited by a receiving housing, which can be inserted, in particular screwed, in the partition wall, wherein said receiving housing permanently accommodates the closing device and into and from said receiving housing the sensor device can be inserted and removed, in particular screwed in and unscrewed. The closing device having its receiving housing in that way forms an adapter, which can be used to attach a sensor device at a selected point of the partition wall contacted by the fluid to be monitored.

The closing plate of the closing device can have a sealing ring on its outer circumference, wherein said sealing ring, in its closed position, is in sealing contact with the receiving housing or with the contact parts assigned to the receiving housing. Under the influence of the closing spring, a safe, fluid-sealed closure of the receiving opening is guaranteed when the sensor device is removed.

In advantageous embodiments, the closing spring of the closing device is a compression spring, one end of which rests against the receiving housing and/or the contact parts and the other end of which rests on a counterholder, which is an integral part of the closing device or can be connected to the closing device.

With regard to the construction of the closing device, the arrangement can be advantageously such that the valve plate and the counterholder are held at a defined distance from each other by means of a web-like connecting piece, which leaves fluid passages open, in particular in the direction of the counterholder, wherein said passages, in conjunction with a further fluid passage of the counterholder, provide a fluid-conveying connection to the sensor of the sensor device via the receiving opening released by means of the closing device. In this way, an installation space is provided for the compression spring along the connecting piece, while at the same time the fluid-conveying connection to the sensor is formed by the fluid passages formed on the connecting piece and on the counterholder.

In an advantageous embodiment, the counterholder has a shell part, which can be connected to the connecting piece of the valve plate and which, open to the receiving opening, forms a receptacle for the facing region of the compression spring, and has foot parts projecting from the shell part in the direction of the sensor device, wherein between said foot parts fluid passages leading from the shell part to the sensor device are formed.

An annular contact part may be attached to the outer end of the receiving housing for supporting the outer end of the compression spring, wherein said annular contact part delimits the receiving opening and forms the sealing surface for the sealing contact of the sealing ring at the valve plate of the closing device.

If the counterholder is formed having a shell part, which can be manufactured as a separate component, a snap-on connection may be provided for its connection to the connecting piece of the valve plate, the snap-on connection permitting a simple assembly procedure by latching it to the connecting piece. Instead of the snap connection, a conventional bayonet lock can also be used.

Below the invention is explained in detail with reference to embodiments shown in the drawing. In the Figures:

FIG. 1 shows a longitudinal section, enlarged by a factor of approximately 6 compared to a practical embodiment, of an embodiment of the device according to the invention, wherein the operating state corresponds to the functional position in which the sensor device is placed in a partition wall, which is only partially indicated;

FIG. 2 shows a longitudinal section corresponding to FIG. 1, wherein the operating state of the inoperative functional position is shown;

FIG. 3 shows a more magnified perspective oblique view of the component of the embodiment forming a closing plate and a counter holder;

FIG. 4 shows a longitudinal section, corresponding to FIG. 1, of a second embodiment, wherein the operating state in the functional position is shown; and

FIG. 5 shows a longitudinal section, corresponding to FIG. 1, of the second embodiment, wherein the operating state in the inoperative functional position is shown.

FIG. 1 shows an embodiment of the sensor device in the operating state of the functional position, wherein the sensor device 1 is inserted in the associated closing device 3. A screw-in part 7, coaxial to the longitudinal axis 9 of the device, of the metal sensor housing 5 of the sensor device 1 is screwed in the threaded section of a central drilled hole 11 in a receiving housing 13 of the sensor device 1. A sealing ring 16, which is located on a step at the end of the screw-in part 7, forms the seal between the sensor housing 5 and the receiving housing 13 of the closing device 3. The receiving housing 13 of the closing device 3 is, as only indicated in FIG. 1, screwed into a threaded hole 15 in a partition wall 17, on the inside 19 of which the fluid to be monitored for impurities is located, wherein, for example, the partition wall 17 delimits a conduit system or a housing through which the fluid flows. A sealing ring 23 is used to seal the screwed-in receiving housing 13 with respect to the outside 21 of the partition wall 17.

Within the sensor housing 5, the sensor 25 of the sensor device 3 has a magnet carrier 27 coaxial with the longitudinal axis 9 and made of metal, wherein said magnet carrier 27 forms a first electrode of the sensor 25 and at the end face, exposed at the end of the screw-in part 7, of said magnet carrier 27 a permanent magnet 31 is held in a receptacle 29 of the magnet carrier 27. The sensor housing 5 has an internal passage which, starting from the free end of the screw-in part 7, has a first section 33 coaxial with the axis 9 and an adjoining second section 35, which extends to the open end 37 of the sensor housing 5. In this passage there is an insulating body 39 in the form of an injection-molded plastic part, for example made from PA6, with which the magnet carrier 27 forming a first sensor electrode and a non-magnetic metal cylinder 41 forming a second sensor electrode are overmolded.

This metal cylinder 41 is embedded in the plastic material of the insulating body 39, coaxial with the axis 9, in such a way that it is exposed at the free end face of the screw-in part 7 and encompasses the likewise exposed end of the magnet carrier 27 forming the first electrode at a small radial distance. The lower end 43, opposite from the end face having the permanent magnet 31, of the magnet carrier 27 insulated from the sensor housing 5 is connected to a source of electrical potential, for example the positive pole of a voltage source, by means of a contact spring not shown. To the lower end, opposite from the upper end face, of the metal cylinder 41 forming the second electrode a drilled hole 45 adjoins, which serves as a passage for the plastic mass. In conjunction with the sealing rings 49 and 51, a metal retaining ring 47 forms the sealed closure at the lower section 35 of the passage of the sensor housing 5, wherein the sealing rings 49 and 51 and the ring body 47 are held by a retaining body 53 made of insulating material, for instance a thermosetting plastic. As with the magnet carrier 27 forming the first electrode, the ring body 47 is also connected to one pole of a voltage source, for example to the negative pole, as symbolically indicated in FIG. 1, via a contact spring device not shown.

The end, open to the inside 19 of the partition 17, of the drilled hole 11 in the receiving housing 13 of the closing device 3 forms the receiving opening 55 for the inlet of the fluid to be monitored. In the end area adjoining the receiving opening 55, the drilled hole 11 is drawn inwards resulting in an end rim reducing the opening diameter being formed, wherein a shoulder surface 57 of said end rim projects radially inwards, forming a contact surface for one end of a compression spring 59. The other end of the latter rests against a counterholder 61, which is located on a closing body 63 of the closing device 3, wherein said closing body 63 is shown separately and enlarged in FIG. 3 and is arranged axially movably in the drilled hole 11 of the receiving housing 13 to form a check valve. As FIGS. 1 and 2 show, the pressure spring 59 is used to hold the counterholder 61 of the closing body 63 in contact with the front face at the end of the screw-in part 7 of the sensor housing 5. In the operating state of the device shown in FIG. 1, in which the sensor housing 5 is fully screwed into the receiving housing 13, the closing body 63 is moved into an open position against the acting spring force, wherein in said open position a valve plate 65 of the closing body 63 is lifted off the receiving opening 55.

FIG. 2 shows an operating condition, in which the sensor housing 5 has been already partially unscrewed from the receiving housing 13 for removal of the sensor housing 5. As a result, the closing body 63 has moved along under the effect of the compression spring 59 until the sealing ring 67, located on the outer circumference, of the valve plate 65 comes into sealing contact with the edge of the receiving opening 55 in the closed position of the valve. As FIG. 3 shows most clearly, the valve plate 65 has an annular groove 71, on the outer circumference below its slightly convex curved upper side 69, as the seat of the sealing ring 67, which is omitted in FIG. 3. A connecting piece 73 extends from the underside of the valve plate 65 as a columnar support of the valve plate 65, wherein webs 75 are formed on the end, opposite from the valve plate 65, of the connecting piece 73, wherein said webs in turn form the support for the counterholder 61. The latter has the shape of an annulus, the outside diameter of which is slightly smaller than the inside diameter of the drilled hole 11 of the receiving housing 13, so that a guide is formed for the sliding movement of the closing body 63. When the closing device 3 is open, the free spaces around the connecting piece 73 and the webs 75 form the fluid passages leading to the sensor 25 via the receiving opening 55.

FIG. 1 shows the operating condition of the functional position for the opened closing device 3. In the course of the operation of the device, when ferromagnetic dirt particles of the fluid entering via the receiving opening 55 are present, the magnetic field generated by the permanent magnet 31 at the sensor 25 results in an accumulation of particles at the front end of the sensor, as indicated in the figures and designated by 26. This accumulation results in an electrical connection between the magnet carrier 27 as the first electrode and the encompassing metal cylinder 41 as the second electrode, depending on the greater or lesser extent of the accumulation 26 and the related level of contamination of the fluid, wherein the decrease in electrical resistance between these electrodes depends on the extent of the presence of metallic particles. When a degree of contamination exceeding a given threshold value is detected and appropriate measures are to be taken, wherein the particle accumulation 26 has to be removed from the sensor 25, the device is moved to the inoperative functional position by unscrewing the sensor housing 5 from the receiving housing 13. FIG. 2 shows the beginning of unscrewing process, wherein the closing body 63 follows the axial movement of the sensor housing 5 under the influence of the compression spring 59 and the valve plate 65 reaches the blocking position closing the receiving opening 55, see FIG. 2, to permit maintenance or replacement measures, such as the removal of the accumulation 26, to be performed without fluid leakage.

The second embodiment shown in FIGS. 4 and 5 differs from the first embodiment mainly by a modified construction of the closing device 3, whereas the sensor housing 5 comprising its associated components is unchanged in comparison to the first example. In contrast to the first embodiment, where the closing body 63 is formed as a one-piece injection molded component made of a plastic material, such as PA6, for instance with glass fiber reinforcement, or made of a metal material, the closing body 63 in the second embodiment is formed bi-partite from such materials. Instead of the counterholder 61, which in the first embodiment is formed directly on the webs 75 of the connecting piece 73, in the second embodiment the counterholder is formed by a shell part 77, which is attached by means of a snap connection to the connecting piece 73 of the closing body 63, which extends in the form of a cylindrical spigot from the valve plate 65. The shell part 77 has the shape of a round shell open in the direction of the valve plate 65, wherein the side wall 79 of the shell is guided axially movable in the drilled hole 11 of the receiving housing 13. A sleeve part 81 extends away from the central area of the shell bottom, wherein said sleeve part 81 surrounds the lower length section of the connecting piece 73 and forms the snap-on connection with inwardly projecting nubs 83, which can be latched to notches in the connecting piece 73. In addition to passages 85 in the bottom of the shell part 77, foot parts 87 extend downwards, which are held in contact with the end face of the sensor 25 at the end of the screw-in part 7 of the sensor housing 5 under the action of the compression spring 59, which rests on the bottom of the shell part 77 as the counterholder. In contrast to the first embodiment, where the contact part for the upper end of the compression spring 59 is formed by a shoulder surface 57 on the receiving housing 13, the present second embodiment is provided with a separate contact part in the form of a annulus 89, which delimits the receiving opening 55 and is attached to the free end edge 91 of the receiving housing 13 by caulking. The annulus 89 forms the sealing surface which, in the closed position of the formed check valve, interacts with the sealing ring 67 on the valve plate 65.

The mode of operation of the second embodiment is equal to that of the first embodiment. As in the first example, where the fluid path from the open receiving opening 55 to the front side of the sensor 25 is routed via the free spaces formed between the webs 75 on the connecting piece 73 of the closing body 63, in the second embodiment a fluid path is formed from the inside of the shell part 77 via the passages 85, formed in the shell bottom, between the base parts 87. For use with fluids at a corresponding pressure level, for example in the range of 10 to 30 bar, preferably 16 bar, the entire housing formed by the screwed together housing parts, the sensor housing 5 and the receiving housing 13, is pressure-resistant and can be made pressure-sealed by means of the sealing elements 16, 23, 49 and 51, wherein stainless steel or zinc coated steel are advantageous housing materials. 

1. A device having a sensor device (1) for detecting a contamination in the form of metal particles in a fluid, which is at least partially encompassed by a partition wall (17), which is at least partially penetrated via a receiving opening (55) by the sensor device (1) arranged in its functional position and comprising its sensor (25) detecting the metal particles, wherein the sensor device (1) can be removed from the partition wall (17) into an inoperative functional position, in particular for maintenance or replacement purposes, characterized in that the sensor device (1) interacts with a closing device (3) such that upon removal of the sensor device (1) to its inoperative functional position, the closing device (3) closes the receiving opening (55) and, in the opposite direction, when the sensor device (1) is brought into its functional position, releases this receiving opening (55).
 2. The sensor device according to claim 1, characterized in that the closing device (3) has a spring-loaded closing plate (65) forming a kind of check valve, wherein said closing plate (65) can be brought into an open position releasing the receiving opening (55) under the action of the sensor device (1) against the action of its closing spring (59) or into its blocking position blocking the receiving opening (55) under the action of the closing spring (59).
 3. The sensor device according to claim 1, characterized in that the receiving opening (55) in the partition wall (17) is delimited by a receiving housing (13), which can be inserted, in particular screwed, in the partition wall (17), wherein said receiving housing (13) permanently accommodates the closing device (3) and into and from said receiving housing (13) the sensor device (1) can be inserted and removed, in particular screwed in and unscrewed.
 4. The sensor device according to claim 1, characterized in that the closing plate (65) of the closing device (3) has a sealing ring (67) on its outer circumference, wherein said sealing ring (67), in its closed position, is in sealing contact with the receiving housing (13) or with the contact parts (89) assigned to the receiving housing (13).
 5. The sensor device according to claim 1, characterized in that the closing spring of the closing device (3) is a compression spring (59), one end of which rests against the receiving housing (13) and/or the contact parts (89) and the other end of which rests on a counterholder (61, 77), which is an integral part of the closing device (3) or can be connected to the closing device (3).
 6. The sensor device according to claim 1, characterized in that the valve plate (65) and the counterholder (61; 77) are held at a defined distance from each other by means of a web-like connecting piece (73), which leaves fluid passages open, in particular in the direction of the counterholder (61; 77), wherein said passages, in conjunction with a further fluid passage (75; 85) of the counterholder (61; 77), provide a fluid-conveying connection to the sensor (25) of the sensor device (1) via the receiving opening (55) released by means of the closing device (3).
 7. The sensor device according to claim 1, characterized in that the counterholder has a shell part (77), which can be connected to the connecting piece (73) of the valve plate (65) and which, open to the receiving opening (55), forms a receptacle for the facing region of the compression spring (59), and has foot parts (87) projecting from the shell part (77) in the direction of the sensor device, wherein between said foot parts (87) fluid passages (85) leading from the shell part (77) to the sensor device (1) are formed.
 8. The sensor device according to claim 1, characterized in that an annular contact part (89) is attached to the outer end of the receiving housing (13) for supporting the outer end of the compression spring (59), wherein said annular contact part (89) delimits the receiving opening (55) and forms the sealing surface for the sealing abutment of the sealing ring (67) on the closing plate (65) of the closing device (3).
 9. The sensor device according to claim 1, characterized in that the shell part (77) is latched to the connecting piece (73) of the valve plate (65) by means of a snap-on connection (83). 